Inspection tools and procedures are commonly implemented during the fabrication of semiconductor devices. Inspection tools are used at various stages of the semiconductor device fabrication process in order to image semiconductor wafers and the lithography masks used to form the patterns on the semiconductor wafers. Fabricating semiconductor devices such as logic and memory devices typically includes processing a substrate such as a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. In some cases, extreme ultraviolet (EUV) and/or deep ultraviolet (DUV) light are used to image the various features of a given mask or wafer. The exposure of an imaging sensor (e.g., CCD imaging sensor) of an inspection tool to EUV or DUV light may lead to degradation of the given imaging sensor. The degradation of one or more imaging sensors of an inspection tool, in turn, leads to reduced processing and analysis throughput.
There are a number of commonly implemented procedures used to mitigate imaging sensor degradation caused by EUV or DUV light. In one case, previous methods included the operation operating an imaging sensor, such as a CCD, at cryogenic temperatures (e.g., below 100 K). However, the cooling of a given imaging sensor serves problematic for large area, high-speed imaging sensors, which are commonly used in commercial applications. The operation of large area, high-speed sensors commonly generates heat at rates greater than 10 W. In turn, this heat generation exerts a significant thermal load on the cryogenic cooling system. This short fall is compounded by the fact that cryogenic cooling systems are typically expensive, large and cumbersome.
In another case, imaging sensor degradation is commonly countered by simply replacing a given imaging sensor once the imaging sensor has reached a selected level degradation or at pre-selected usage levels based on anticipated degradation. This technique, however, leads to increased downtime of the given inspection tool, reducing efficiency and throughput.
As a result, improved systems and methods for mitigating the impact of image sensor degradation caused by exposure to EUV or DUV light are desirable.